1. Field of the Invention
The present invention relates to a display apparatus using a lens sheet that, by the refraction action of a unit columnar lens or a unit lens, provides increased widening of light from a display panel.
2. Description of the Related Art
In a display device, and particularly in a liquid-crystal display device, the contrast at the viewing line of an observer thereof is lowered at an inclination from the normal direction to the screen, in comparison with the contrast at the normal direction, leading to problems such as a lowering of the visibility of the screen.
In recent years, with an increase in the screen size of liquid-crystal displays, there has been a desire to improve the visibility of the screen when it is viewed at an inclination. Based on this desire, and as disclosed, for example, in Japanese Unexamined Patent Application publication H5-249453, there has been proposed the use of a microlens array on the observed side of a liquid-crystal display, so as to broaden the viewing angle.
FIG. 18 shows an example of a lenticular lens sheet 1 of the past. A typical configuration is one with what are called black stripes, wherein light from an incident light surface is collected by a lens part 2 formed by lenticular lenses or the like, the focal point region of the lens part 2 being made the light-exiting surface, on a part of which are formed light non-exiting parts (black stripes) 3, so that light is diffused and the influence of external light is reduced. Because this type has black stripes 3, when laminated with a device having, for example, the matrix of a liquid-crystal display, there is a particular tendency for a fringe pattern caused by the Moire effect to occur, making it particularly necessary to have a means of suppressing this stripe pattern.
As disclosed in the above-noted Japanese Unexamined Patent Application publication H5-249453, a sheet onto one side of which only is formed a microlens array is provided on the observation side of the liquid-crystal display element, with the side opposite the microlenses on the observation side and, while this broadens the viewing angle, external light is totally reflected by the microlenses, so that the sheet itself appears to shine, thereby actually leading to a lowering of the contrast.
When using a lenticular lens as a microlens array in display having a matrix formed on the surface thereof, such as a liquid-crystal display (LCD), a plasma display panel (PDP), an electroluminescent display (ELD), or a field emission display (FED) or the like, depending upon the positional relationship between the lenticular lens and the matrix, there was the problem of Moire fringes being observed on the screen. Additionally, depending upon the distance between the microlens array and the display device, there was the problem that the display could actually become more difficult to view.
A problem pointed out as occurring when using a lenticular lens sheet having black stripes as a viewing angle widening sheet for a display was that, if the exiting angle of light from the display is wide, the collection of light at the lens part does not function well, absorption occurring in the black stripes, thereby reducing the efficiency.